Devices such as specialized semiconductor optical amplifiers require mirror quality sidewalls, and the success of these devices is strongly dependent on reflectivity of the mirror surface. With the combination of optimized mirror design and crystal growth, and the use of anisotropic ion etching, micron-sized optical microresonators have been fabricated. These capabilities are now also applied to electrically and optically pumped surface-emitting microlasers and other vertical-cavity devices. In order to define the deep structures needed for these applications, highly anisotropic and nonselective ion etching processes must be optimized. Furthermore, improved masking techniques must be devised to produce low-resistance contacts for electrically pumped structures. Chemically assisted ion beam etching (CAIBE), a technique in which the sample is simultaneously subjected to both an ion beam and a reactive gas flux, has been demonstrated to be an extremely anisotropic pattern transfer method. The capabilities of this technique are ideal for solving the problems associated with microfabrication of semiconductor devices, such as vertical-emitting semiconductor lasers, and has already replaced cleaving techniques for making high quality mirror finish sidewalls. For III-V materials, facets can be cleaved in two orthogonal directions along preferred crystal directions. Whereas CAIBE etching can be done anywhere and practically any shape structure can be made including mesas, ridges and wells.
However, new or modified fabrication techniques which are used to produce optically and electrically pumped laser and microresonator arrays are still being sought. A technique known as dry etching can make smooth mirror quality etched surfaces, as well as depth and verticality requirements to semiconductor devices.